From d6693160906d55ba376bf0b88b7c129762170162 Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Tue, 9 Jan 2018 23:11:03 +0100 Subject: [PATCH] ALSA: seq: Make ioctls race-free commit b3defb791b26ea0683a93a4f49c77ec45ec96f10 upstream. The ALSA sequencer ioctls have no protection against racy calls while the concurrent operations may lead to interfere with each other. As reported recently, for example, the concurrent calls of setting client pool with a combination of write calls may lead to either the unkillable dead-lock or UAF. As a slightly big hammer solution, this patch introduces the mutex to make each ioctl exclusive. Although this may reduce performance via parallel ioctl calls, usually it's not demanded for sequencer usages, hence it should be negligible. Reported-by: Luo Quan Reviewed-by: Kees Cook Reviewed-by: Greg Kroah-Hartman Signed-off-by: Takashi Iwai [bwh: Backported to 3.2: ioctl dispatch is done from snd_seq_do_ioctl(); take the mutex and add ret variable there.] Signed-off-by: Ben Hutchings --- Reading git-format-patch failed